Phase-coherent Electron Transport Research Articles

Spatial distribution of current and Fermi carriers around localized elastic scatterers in quantum transport.

The two-dimensional spatial distribution of the current and Fermi carriers around localized elastic scatterers in phase-coherent electron transport has been calculated using a generalized scattering-matrix approach. The distributions show dramatic differences depending on whether the scatterers are attractive (donorlike) or repulsive (acceptorlike). We find that attractive scatterers can produce strong vortices in the current, resulting in localized magnetic moments, while repulsive scatterers produce much weaker vortices and may not produce any at all in quasiballistic transport (few impurities). This is a significant difference between majority-carrier transport (when the scatterers are attractive) and minority-carrier transport (scatterers are repulsive). The vortices are caused by quantum-mechanical interference between scatterers and are accentuated by evanescent modes which have a stronger effect in the case of attractive scatterers owing to the formation of quasidonor states. We also examine the influence of the impurity configuration (positions of the scatterers) on the nature of the vortices.

Quantum transport in a disordered nanostructure in the presence of a magnetic field

We have studied phase coherent electron transport in a disordered semiconductor quantum wire subjected to a weak magnetic field. Our model treats disorder (elastic scattering) with scattering matrices and uses Weber functions to calculate the elements of the scattering matrices. The Weber functions account for the magnetic field exactly. We find that the universal conductance fluctuations and the two-terminal Landauer resistance of a disordered structure are surprisingly sensitive to whether the scatters are attractive or repulsive and the difference between the effects of attractive and repulsive scatterers is accentuated by the presence of evanescent states.

The role of evanescent states in quantum transport through disordered mesoscopic structures

The influence of evanescent states on phase-coherent electron transport through disordered mesoscopic structures is examined. These states are found to play a critical role in transport, especially if the structures are heavily disordered and the scattering potentials are attractive, rather than repulsive. We present results from our study of the effect of evanescent states on Anderson localization and conductance fluctuations in disordered semiconductor nanostructures.

Scattering matrix analysis of electron transport in disordered Aharonov–Bohm interferometers and ballistic constrictions

We present a fully quantum-mechanical analysis of phase-coherent electron transport in disordered semiconductor nanostructures. The analysis is based on a scattering matrix formalism which allows us to simulate the effects of interface roughness scattering, as well as scattering from point defects and defect clusters. Using this technique, we have studied quantum conduction in electrostatic Aharonov–Bohm interferometers and narrow ballistic constrictions of submicron dimensions.